Levels and health risk assessments of heavy metals in urban soils in Dongguan, China

Human body may be directly exposed to heavy metals in urban soils through oral ingestion, dermal contact, and inhalation of soil particles. A total of 170 topsoil samples were collected from the urbanized area of Dongguan, China. Concentrations of As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, and Zn in soils were measured to calculate enrichment factors (EFs), pollution indexes (PIs), carcinogenic risks (CRs), and hazard indexes (HIs) of these elements. The mean concentrations of every element in urban soils of Dongguan are lower than both the soil environmental quality standards of China and the Canadian soil quality guidelines. However, concentrations of Cd, Cu, Ni, and Zn have increased slightly in the past 20years. Slight contamination was observed in some samples for all heavy metals according to the Chinese soil quality standards, and the element of As may be the most important contaminant. Furthermore, the element of As may pose both carcinogenic and non-carcinogenic risks to human health. Oral ingestion and inhalation of soil particles are the main exposure pathways of As to the human body. This study may provide a scientific basis for strategies to protect human health in urban areas. •Cd, Cu, Ni and Zn increased in the soils over the past 20years.•Despite slight contamination of those metals, urban soils were relatively clean.•Arsenic in urban soils is the most harmful contaminant to human health.•Oral ingestion and inhalation are the main exposure pathways of arsenic for humans.